You will need at least two partitions.
2
Two. One for Windows XP and one for Windows Vista.
The minimum number of partitions needed to dual boot windows xp and windows vista is actually 2, one for each operating system. However, if your computer was bought and it already had one of those two systems preinstalled and with it a separate windows recovery partition as well as a system reserved partition, then your minimum in that case would be 4 priamry partitions (which also happens to be the maximum allowed if you are using strictly primary partitions. One way to have more than 4 primary partitions is to have one of those partitions become an extended partition which can in turn have as many partitions as you need. I hope that wasn't too confusing
two
60 Logical partitions can be created. Only 26 are reachable in Windows Due to the number of letters in thealphabet.
4.
Windows XP Professional Install is about 3.7GB on my system using VMware
A technician is attempting to create multiple partitions on a hard disk. This will allow for storing the operating system and data files on separate partitions. What is the maximum number of primary partitions per hard drive that is supported by Windows XP?
Disk Management
It should have the same limitations as any other operating system if you solely work with physical volumes - 4 primary partitions on MBR, unlimited on GPT (though Windows will limit it to 128). Otherwise, if you use something like LVM, it would be unlimited logical partitions, across a single disk or multiple disks.
There's a limit to the number of primary partitions per drive, 4. In order to get more than 4 drives out of one (if this takes your fancy) then you use an extended partition. To a low level program which doesnt speak fluent windows, everything on your extended partition appear as a single drive. Other than this their is no real advantage to extended partitions over primary partitions, but at windows level no significant disadvantage either
There can be any number of drives in Windows Explorer. The minimum number of drives is one (for the primary partition Windows is installed on).